Flexible Circuit Push-Button for Wristwatch Fatigue Resistance
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Solution Overview
Problem
Existing push-button arrangements in portable devices like wristwatches are bulky and prone to fatigue due to shear stress on welds, which affects their mechanical resistance and integration in small devices.
Innovation Solution
A surface-mounted push-button arrangement with a flexible printed circuit sheet folded around the edge of an electronic plate, where the push-button is soldered flat, reducing shear stress on welds and enhancing mechanical resistance, and housed within a plate with auxiliary support to limit movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional elastic blade push-button is used, then the push-button can be held in rest position and produce a click, but the device becomes bulky and the welds are prone to fatigue
Solution Approach 1:
The patent replaces the traditional mechanical elastic blade system with an electronic solution. A flexible printed circuit board with an elastic circuit trace replaces the mechanical elastic blade, and electrical contacts replace the mechanical click feedback. This substitution eliminates the need for a long mechanical blade while maintaining the push-button function, thereby reducing size and improving fatigue resistance of welds.
Solution Approach 2:
The patent changes the material parameters by using a flexible printed circuit board with an elastic circuit trace instead of a rigid mechanical blade. The elastic circuit trace provides the necessary elasticity through its conductive path design rather than through a mechanical blade structure, allowing for a more compact design with better fatigue resistance.
2Ease of operation
If the push-button support is mounted cantilevered with spot welds, then the push-button can be positioned, but the welds are subjected to shear stress and may give way due to fatigue
Solution Approach 1:
The patent replaces the mechanical spot weld support structure with an integrated flexible printed circuit board mounting system. The elastic circuit trace is soldered to the electronic board, distributing stresses over a larger area and eliminating the cantilevered spot weld configuration that was prone to fatigue failure.
3Volume of moving object
If a surface-mounted push-button with flexible metal sheet dome is used, then the device takes up less space, but the support structure requires welds that are prone to shear stress
Solution Approach 1:
The patent replaces the rigid flexible metal sheet dome with an elastic circuit trace on a flexible printed circuit board. This maintains the compact size advantage while eliminating the need for a cantilevered support structure with spot welds, as the elastic trace is integrated into the flexible circuit board which can be soldered more robustly to the electronic board.
4Strength
If the elastic blade extends in one plane, then it can restore user effort, but it must be long enough which increases the size of the arrangement
Solution Approach 1:
The patent replaces the long mechanical elastic blade with an elastic circuit trace on a flexible printed circuit board. The elastic circuit trace provides the necessary restoring force through its conductive path elasticity rather than through a long mechanical blade, achieving the same function in a much more compact form factor.
Solution Approach 2:
The patent changes the physical form of the elastic element from a mechanical blade to an electrical circuit trace. The elastic properties are maintained through the conductive material and trace geometry rather than through mechanical blade dimensions, allowing for a compact design that retains the necessary elastic restoring force.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution results in a compact, fatigue-resistant push-button design that is easier to manufacture and integrate into small devices, with improved mechanical resistance and positioning tolerances.
Implementation Method 1
elastic means which push the head of the rod towards outside
Implementation Method 2
The elastic means are for example formed by a helical spring housed in the through passage and which bears between the frame and the head of the pusher
Implementation Method 3
the dome having a rim resting on a first contact and a top which, when the user presses the push-button, deforms and presses against a second contact
Implementation Method 4
mounted cantilevered by one of its branches 6a on the upper surface 8 of the electronic plate 2 by means of a few spot welds 10
Data Source
Figure 1~4
AI summary
Pushbutton arrangement comprising an electronic board (18), the pushbutton (30) being of the type mounted on the surface of a flexible printed circuit board (26) itself partially fixed on the electronic board (18), a portion (28) of the flexible printed circuit board (26) which carries the pushbutton (30) remaining free and being folded around a peripheral edge (20) of the electronic board (18) so that the pushbutton (30) extends substantially perpendicularly to the electronic board (18), bearing against a lateral surface (22) of this electronic board (18).